Email Delivery Explained!

Sending and receiving email is similar to traditional mail.

Mail Box

To send a letter through the mail it requires a “to” and “from” address. The “to” address directs the letter to its destination, and the “from” address can be used in case the mail is returned. In the digital world, a mail exchanger (MX) server can be used to send and receive email.

The MX server has specialized software for distributing mail. To determine the destination of the email, the mail delivery agent (MDA) reads the header and determines if the email should remain on its own server or send over the internet to a remote server. The MDA takes the place of the postal worker, in this case, it looks at the “to” and “from” addresses and determines if it can be delivered locally or placed on a truck and sent across state lines

To accomplish this, the MDA uses two specifications, the address record (A Record) and the mail exchange record (MX) record. The A record takes the domain of the host and translates it into an IP address that an email can be sent to. The mail exchange record includes the hostname for the domain as well as a code that prioritizes the email. The lower the code number the higher the priority. Incoming emails are routed through the IP address as assigned in the A record.

An example of these records is below.

A Record: MX Record:

Domain: Dundee.net

Host Name: Mail

IP: 11.11.11.222

Domain: Dundee.net

Mail exchange: mail.dundee.net

Priority:10

So, how do these internal records affect your emails being sent? Let’s look at a specific example, you are mailing your welcome letter to your new member, his email address is Freeman@dundee.net. The mail delivery agent looks at the domain, in this case, it is Dundee.net and compares it to the A record. The A record converts the domain into an IP address where the email will be sent. Next, the MX record is used to redirect the email to the mail host and tells the host what priority the email is. The email is then sent using these guidelines and reaches its destination where it is opened.